C. Peter Wolk

Bio: C. Peter Wolk is an academic researcher from Michigan State University. The author has contributed to research in topics: Heterocyst & Anabaena. The author has an hindex of 38, co-authored 83 publications receiving 5066 citations. Previous affiliations of C. Peter Wolk include Great Lakes Bioenergy Research Center.

Complete genomic sequence of the filamentous nitrogen-fixing cyanobacterium Anabaena sp. strain PCC 7120

Abstract: The nucleotide sequence of the entire genome of a filamentous cyanobacterium, Anabaena sp. strain PCC 7120, was determined. The genome of Anabaena consisted of a single chromosome (6,413,771 bp) and six plasmids, designated pCC7120α (408,101 bp), pCC7120β (186,614 bp), pCC7120γ (101,965 bp), pCC7120δ (55,414 bp), pCC7120e (40,340 bp), and pCC7120ζ (5,584 bp). The chromosome bears 5368 potential protein-encoding genes, four sets of rRNA genes, 48 tRNA genes representing 42 tRNA species, and 4 genes for small structural RNAs. The predicted products of 45% of the potential protein-encoding genes showed sequence similarity to known and predicted proteins of known function, and 27% to translated products of hypothetical genes. The remaining 28% lacked significant similarity to genes for known and predicted proteins in the public DNA databases. More than 60 genes involved in various processes of heterocyst formation and nitrogen fixation were assigned to the chromosome based on their similarity to the reported genes. One hundred and ninety-five genes coding for components of two-component signal transduction systems, nearly 2.5 times as many as those in Synechocystis sp. PCC 6803, were identified on the chromosome. Only 37% of the Anabaena genes showed significant sequence similarity to those of Synechocystis, indicating a high degree of divergence of the gene information between the two cyanobacterial strains.

Heterocyst Metabolism and Development

Abstract: Heterocysts are differentiated cells that are specialized for fixation of N2 in an aerobic environment. In heterocysts in the light, Photosystem I generates ATP, but no photosynthetic production of O2 takes place. Instead, reductant moves into heterocysts from vegetative cells. In return, fixed nitrogen moves from heterocysts to vegetative cells. In neither case is there certainty about the identity of the traffic molecules. Pathways of electron-donation to N2 have been extensively investigated, but their in-vivo importance remains to be critically tested. Nitrogenase in heterocysts is protected from inactivation by O2 by a variety of means, principally by enhanced respiration and by a barrier, the heterocyst envelope, to entry of O2. However, the respiratory apparatus and the biosynthetic processes that result in synthesis of the barrier have been little studied. The detailed mechanisms underlying metabolic, environmental, and developmental control of nitrogenase are under investigation. Studies of heterocyst development are being greatly facilitated by recent advances in the genetics of Anabaena sp. An autoregulated gene, hetR, that is activated shortly after nitrogen-stepdown is critical for the differentiation of heterocysts. Two enigmas remain to be answered: how is it determined which cells will differentiate; and, after differentiation is initiated, what intercellular interactions and intracellular mechanisms regulate the progression of the differentiation process? An evolutionary and biochemical relationship between the processes leading to the formation of heterocysts and akinetes is suggested.

Spatial expression and autoregulation of hetR, a gene involved in the control of heterocyst development in Anabaena

Abstract: The spatially patterned differentiation of heterocysts in the filamentous cyanobacterium Anabaena requires a functional hetR gene. Transcriptional fusions to luxAB show that hetR is transcribed at a low level throughout the filament when Anabaena is grown with combined nitrogen, and that induction of the gene begins within 2 h following nitrogen deprivation. By 3.5 h, induction is localized to spaced foci. By 6 h, there is an overall induction of at least threefold in whole cultures, reflecting at least a 20-fold increase within spatially separated cells. The induction requires the presence of a functional hetR gene, indicating that hetR is autoregulatory. Full induction of a heterocyst structural gene, hepA, also requires a functional hetR locus.

Movement of Carbon from Vegetative Cells to Heterocysts in Anabaena cylindrica

Abstract: Radioactive carbon assimilated by vegetative cells of Anabaena cylindrica in the light passed via an intrafilamentous route into heterocysts in the dark. After several hours, label per heterocyst approximated label per vegetative cell. Much of the label entering heterocysts was not available for diffusional exchange back into vegetative cells.

Fischerellin, a new allelochemical from the freshwater cyanobacterium Fischerella Muscicola

Abstract: The benthic cyanobacterium Fischerella muscicola (Thur.) Gom. UTEX 1829 produces a secondary metabolite, fischerellin, that strongly inhibits other cyanobacteria and to a lesser extent members of the Chlorophyceae. Eubacteria are not affected. The major active compound is lipophilic and exhibits a molecular ion at m/z 408. It is heat- and acid-stable but decomposes in 1 M sodium hydroxide (80° C. 1 h). Fischerellin inhibits the photosynthetic but not the respiratory electron transport of cyanobacteria and chlorophytes. Its site of action is located in PS II. Two other species of Fischerella also produce fischerellin, indicating that the synthesis of such allelochemicals might be characteristic of the genus.

Proceedings of the National Academy of Sciences

Abstract: where A represents the magnetic vector potential, is an integral of the hydromagnetic equations. This -integral made it possible to formulate a variational principle for the force-free magnetic fields. The integral expresses the fact that motions cannot transform a given field in an entirely arbitrary different field, if the conductivity of the medium isconsidered infinite. In this paper we shall show that the full set of hydromagnetic equations admit five more integrals, besides the energy integral, if dissipative processes are absent. These integrals, as we shall presently verify, are I2 =fbHvdV, (2)

The Effects of Harmful Algal Blooms on Aquatic Organisms

Abstract: (2002). The Effects of Harmful Algal Blooms on Aquatic Organisms. Reviews in Fisheries Science: Vol. 10, No. 2, pp. 113-390.

The penicillin-binding proteins: structure and role in peptidoglycan biosynthesis

Abstract: Penicillin-binding proteins (PBPs) have been scrutinized for over 40 years. Recent structural information on PBPs together with the ongoing long-term biochemical experimental investigations, and results from more recent techniques such as protein localization by green fluorescent protein-fusion immunofluorescence or double-hybrid assay, have brought our understanding of the last stages of the peptidoglycan biosynthesis to an outstanding level that allows a broad outlook on the properties of these enzymes. Details are emerging regarding the interaction between the peptidoglycan-synthesizing PBPs and the peptidoglycan, their mesh net-like product that surrounds and protects bacteria. This review focuses on the detailed structure of PBPs and their implication in peptidoglycan synthesis, maturation and recycling. An overview of the content in PBPs of some bacteria is provided with an emphasis on comparing the biochemical properties of homologous PBPs (orthologues) belonging to different bacteria.

Applications of the acetylene-ethylene assay for measurement of nitrogen fixation

Abstract: A comprehensive report of the acetylene reduction assay for measurement of N2 fixation is presented. The objective is to facilitate the effective use and identify some potential limitations of the method. The report is based on more than 200 accounts of the use of this technique in 15 countries during the last 5 years. Methods of measurement of N2 fixation are compared. Nomenclature, e.g., N2[C2H2] fixed, is introduced to identify values of N2 fixation determined by C2H2-C2H2 assay. The biochemical basis of the assay is described along with relevant characteristics including Km, C2H2/N2 conversion factor, and specific N2[C2H2]-fixing activities obtained with various systems. Effects of combined nitrogen, temperature, light, pO2, N2, pC2H2 and water on activity are summarized. Available methods for sample preparation, assay chamber, gas phase, assay condition, termination of reaction, C2H4 analysis and expression of results are compared. The many uses of the C2H2-C2H4 assay for investigations of the biochemistry of nitrogenase and physiology of N2-fixing organisms, definition of N2-fixing organisms and measurement of field N2 fixation by legume, non-legume, soil, marine, rhizosphere, phylloplane and mammalian samples are tabulated.

Engineering herbicide resistance in plants by expression of a detoxifying enzyme.

Abstract: Phosphinothricin (PPT) is a potent inhibitor of glutamine synthetase in plants and is used as a non-selective herbicide. The bar gene which confers resistance in Streptomyces hygroscopicus to bialaphos, a tripeptide containing PPT, encodes a phosphinothricin acetyltransferase (PAT) (see accompanying paper). The bar gene was placed under control of the 35S promoter of the cauliflower mosaic virus and transferred to plant cells using Agrobacterium-mediated transformation. PAT was used as a selectable marker in protoplast co-cultivation. The chimeric bar gene was expressed in tobacco, potato and tomato plants. Transgenic plants showed complete resistance towards high doses of the commercial formulations of phosphinothricin and bialaphos. These data present a successful approach to obtain herbicide-resistant plants by detoxification of the herbicide.